life science

GRADE 9 LIFE SCIENCES STUDY NOTES (Simple Version)

💫 BIOLOGICAL TERMS

  • What protects the heart? ➤ The ribs

  • Membrane
    ➤ A thin wall around the cell.
    ➤ It lets some things in and out.
    ➤ Helps control what enters and leaves the cell.

📊 GRAPHS & TABLES

✅ Table Rules

  • Draw the table neatly

  • Close all the boxes

  • Give the table a heading

  • Left column: What you change (independent variable)

  • Right column: What you measure (dependent variable)

  • Write units in brackets, not in the headings

✅ Graph Rules

  • Write a heading with both variables

  • X-axis: What you change (independent variable)

  • Y-axis: What you measure (dependent variable)

  • Use a ruler

  • Keep the scale even

  • Write units in brackets

📈 Types of Graphs

  • Bar Graph
    ✔ Used for different groups (not continuous data)
    ✔ Bars have spaces between them
    ✔ Good for comparing things

  • Histogram
    ✔ Used for numbers in ranges (like 0–10, 11–20)
    ✔ Bars are touching
    ✔ Shows how often something happens

  • Line Graph
    ✔ Used to show change over time
    ✔ Plot dots and connect with lines
    ✔ Good for showing trends

🧹 VARIABLES IN EXPERIMENTS

  • Independent Variable: What you change

  • Dependent Variable: What you measure

  • Control Variable: What stays the same

📃 DATA TYPES

Qualitative Data

Quantitative Data

No numbers

Has numbers

No units

Has units (kg, cm, g, etc.)

Not exact

Exact

Based on opinion

Based on facts

Example: colour, texture

Example: mass, length

🔧 USING A MICROSCOPE

  • Carry with two hands (base and arm)

  • Keep it covered when not used

  • Don’t touch the lenses

  • Start with the lowest lens

  • Focus using big knob (coarse), then small knob (fine)

  • Adjust light using diaphragm

Magnification = Eyepiece × Objective lens
Example: 10x × 40x = 400x

Wet Mount Slide:

  • Place drop of water on slide

  • Put specimen in the water

  • Add cover slip carefully

  • Blot extra water with tissue

Good Things:

  • Quick

  • Can see living things

  • Natural colours

Bad Things:

  • Water dries fast

  • Objects move

  • Can't keep the slide long

💚 CELLS

  • Cells are the basic building blocks of life

  • All living things are made of cells

Two Main Cell Types

  • Prokaryotic: No nucleus (e.g. bacteria)

  • Eukaryotic: Has a nucleus (e.g. plant and animal cells)

Parts of a Cell

  • Nucleus: Controls the cell

  • Cytoplasm: Jelly inside the cell

  • Cell Membrane: Outside layer, controls what goes in and out

  • Vacuole: Stores water and food

  • Mitochondrion: Gives energy

  • Chloroplast: Makes food in plant cells

Plant vs Animal Cells

Feature

Plant Cell

Animal Cell

Cell Wall

Yes

No

Shape

Box-shaped

Irregular shape

Vacuole

One big vacuole

Small or none

Chloroplast

Yes

No

Lysosomes

No

Yes

🔢 CELL DIVISION

Mitosis

  • Happens in body cells

  • Makes 2 cells that are the same

  • Used for growth and repair

Meiosis

  • Happens in sex cells (sperm and egg)

  • Makes 4 cells that are all different

  • Used for reproduction

Why Cells Divide:

  • To grow

  • To fix damage

  • For making babies in animals/plants

⚠ CANCER

  • Happens when cells keep dividing in the wrong way

Types of Tumours

  • Benign: Not dangerous, stays in one place

  • Malignant: Dangerous, can spread

What Can Cause Cancer:

  • Inherited from family

  • Too much sun

  • X-rays

  • Smoking

  • Hormones

  • Chemicals and viruses

  • Stress

Treatment

  • Surgery: Remove cancer

  • Chemotherapy: Medicine to kill cells

  • Radiation: Use rays to kill cells



  • Immunotherapy: Uses the body’s immune system to fight cancer.